A well-prepared scout never goes anywhere without his trusty Swiss army knife. Similarly, you need a portable arsenal of troubleshooting tools to solve common computer problems. You never know when your laptop, or a friend's computer, may start acting up. Load up these free tech support utilities onto a USB flash drive and they'll think you're a tech support superhero!
All of these handy programs are free, but they also share another important common factor. They don't require any installation, because they're designed to be portable. The ability to run them directly from the USB drive is important for several reasons. First, on a badly infected system, sometimes you can't even install new software. A virus may be blocking the introduction of new software, or the Windows installer may be broken. Also, some programs require administrator privileges to install, which presents a hurdle if the admin password is unknown.
To see all programs and links to download take a gander over to Ask Bob Rankin.